1. Field of the Invention
The present invention relates to a process and apparatus for controlling the force on a moving web of material. More specifically, it relates to a process and apparatus for taking a web of material from a container and adjusting its width by controlling the force exerted on the web.
2. The Prior Art
Processing webs of material taken from supply containers is known in the art. The web of material must be spread out and properly guided and aligned throughout the apparatus in order to be treated or wound onto a take-up reel. Spreading rolls are provided to eliminate folds as the web exits the supply container. Guiding and breadth-stretching rolls are also provided if the material web has to be guided during spreading in a certain direction, or if its direction of travel has to be corrected. However, a drawback exists in that the web which has been spread on the breadth-stretching roll or batten roll will retract to a narrower width before it is received by a fixing roll which stabilizes the width of the web. The extent to which the web retracts or is overstretched depends on the force with which the web of material is pulled across the batten roll to the fixing roll.
The batten roll is rotated based on the adhesion of the web material as it travels across the batten roll. The web is smoothed by lateral movement of the batten roll, depending on the condition and direction of travel of the web as it moves across the batten roll. In this type of arrangement, different forces are continually exerted on the web, which leads to considerable stress on the fabric. This results in a completely distorted web of fabric which adversely affects the further treatment and processing of the material web.
One attempt to avoid the application of excessive loads to a roll of material is described in U.S. Pat. No. 4,632,325 to Feyerl et al. Feyerl provides an apparatus for unwinding a web from a roll including a roll bearing for supporting the roll. A controller positions the roll with respect to the roll bearing to avoid an application of excessive loads to the web. However, Feyerl cannot be used with a web which is being drawn from a container. Also, Feyerl does not provide means for adjusting the width of the web after it is unwound from the roll.